1、ACI 207.1R-05 supersedes ACI 207.1R-96 and became effective December 1, 2005.Copyright 2006, American Concrete Institute.All rights reserved including rights of reproduction and use in any form or by anymeans, including the making of copies by any photo process, or by electronic ormechanical device,
2、 printed, written, or oral, or recording for sound or visual reproductionor for use in any knowledge or retrieval system or device, unless permission in writingis obtained from the copyright proprietors.ACI Committee Reports, Guides, and Commentaries areintended for guidance in planning, designing,
3、executing, andinspecting construction. This document is intended for the useof individuals who are competent to evaluate the significanceand limitations of its content and recommendations and whowill accept responsibility for the application of the material itcontains. The American Concrete Institut
4、e disclaims any andall responsibility for the stated principles. The Institute shallnot be liable for any loss or damage arising therefrom.Reference to this document shall not be made in contractdocuments. If items found in this document are desired by theArchitect/Engineer to be a part of the contr
5、act documents, theyshall be restated in mandatory language for incorporation bythe Architect/Engineer.1Guide to Mass ConcreteReported by ACI Committee 207ACI 207.1R-05(Reapproved 2012)Mass concrete is any volume of concrete with dimensions large enough torequire that measures be taken to cope with t
6、he generation of heat fromhydration of the cement and attendant volume change to minimize cracking.The design of mass concrete structures is generally based on durability,economy, and thermal action, with strength often being a secondary concern.This document contains a history of the development of
7、 mass concretepractice and discussion of materials and concrete mixture proportioning,properties, construction methods, and equipment. It covers traditionally placedand consolidated mass concrete and does not cover roller-compacted concrete.Keywords: admixture; aggregate; air entrainment; batch; cem
8、ent; compressivestrength; cracking; creep; curing; durability; fly ash; formwork; grading;heat of hydration; mass concrete; mixing; mixture proportion; modulusof elasticity; placing; Poissons ratio; pozzolan; shrinkage; strain; stress;temperature rise; thermal expansion; vibration; volume change.CON
9、TENTSChapter 1Introduction and historical developments, p. 21.1Scope1.2History1.3Temperature control1.4Long-term strength designChapter 2Materials and mixture proportioning, p. 52.1General2.2Cements2.3Pozzolans and ground slag2.4Chemical admixtures2.5Aggregates2.6Water2.7Selection of proportions2.8T
10、emperature controlChapter 3Properties, p. 123.1General3.2Strength3.3Elastic properties3.4Creep3.5Volume change3.6Permeability3.7Thermal properties3.8Shear properties3.9DurabilityChapter 4Construction, p. 194.1Batching4.2Mixing4.3Placing4.4Curing4.5Forms4.6Height of lifts and time intervals between l
11、ifts4.7Cooling and temperature control4.8Instrumentation4.9Grouting contraction jointsJeffrey C. Allen Robert W. Cannon John R. Hess Tibor J. PatakyTerrence E. Arnold Teck L. Chua Rodney E. Holderbaum Steven A. RaganRandall P. Bass Eric J. Ditchey Allen J. Hulshizer Ernest K. SchraderJ. Floyd Best T
12、imothy P. Dolen David E. Kiefer Gary P. WilsonAnthony A. Bombich Barry D. Fehl Gary R. MassStephen B. TatroChair207.1R-2 ACI COMMITTEE REPORTChapter 5References, p. 207.1R-275.1Referenced standards and reports5.2Cited referencesCHAPTER 1INTRODUCTIONAND HISTORICAL DEVELOPMENTS1.1ScopeMass concrete is
13、 defined in ACI 116R as “any volume ofconcrete with dimensions large enough to require thatmeasures be taken to cope with generation of heat fromhydration of the cement and attendant volume change tominimize cracking.” The design of mass concrete structuresis generally based on durability, economy,
14、and thermalaction, with strength often being a secondary, rather than aprimary, concern. The one characteristic that distinguishesmass concrete from other concrete work is thermal behavior.Because the cement-water reaction is exothermic by nature,the temperature rise within a large concrete mass, wh
15、ere theheat is not quickly dissipated, can be quite high. Significanttensile stresses and strains may result from the restrainedvolume change associated with a decline in temperature asheat of hydration is dissipated. Measures should be takenwhere cracking due to thermal behavior may cause a loss of
16、structural integrity and monolithic action, excessive seepageand shortening of the service life of the structure, or beaesthetically objectionable. Many of the principles in massconcrete practice can also be applied to general concretework, whereby economic and other benefits may be realized.This do
17、cument contains a history of the development ofmass concrete practice and a discussion of materials andconcrete mixture proportioning, properties, constructionmethods, and equipment. This document covers traditionallyplaced and consolidated mass concrete, and does not coverroller-compacted concrete.
18、 Roller-compacted concrete isdescribed in detail in ACI 207.5R.Mass concreting practices were developed largely fromconcrete dam construction, where temperature-relatedcracking was first identified. Temperature-related crackinghas also been experienced in other thick-section concretestructures, incl
19、uding mat foundations, pile caps, bridge piers,thick walls, and tunnel linings.High compressive strengths are usually not required in massconcrete structures; however, thin arch dams are exceptions.Massive structures, such as gravity dams, resist loads primarilyby their shape and mass, and only seco
20、ndarily by their strength.Of more importance are durability and properties connectedwith temperature behavior and the tendency for cracking.The effects of heat generation, restraint, and volumechanges on the design and behavior of massive reinforcedelements and structures are discussed in ACI 207.2R
21、.Cooling and insulating systems for mass concrete areaddressed in ACI 207.4R. Mixture proportioning for massconcrete is discussed in ACI 211.1.1.2HistoryWhen concrete was first used in dams, the dams wererelatively small and the concrete was mixed by hand. Theportland cement usually had to be aged t
22、o comply with aboiling soundness test, the aggregate was bank-run sand andgravel, and proportioning was by the shovelful (Davis 1963).Tremendous progress has been made since the early 1900s,and the art and science of dam building practiced today hasreached a highly advanced state. Presently, the sel
23、ection andproportioning of concrete materials to produce suitablestrength, durability, and impermeability of the finishedproduct can now be predicted and controlled with accuracy.Covered herein are the principal steps from those verysmall beginnings to the present. In large dam construction,there is
24、 now exact and automatic proportioning and mixingof materials. Concrete in 12 yd3(9 m3) buckets can be placedby conventional methods at the rate of 10,000 yd3/day(7650 m3/day) at a temperature of less than 50 F (10 C) asplaced, even during extremely hot weather. Grand CouleeDam still holds the all-t
25、ime record monthly placing rate of536,250 yd3(410,020 m3), followed by the more recentachievement at Itaipu Dam on the Brazil-Paraguay border of440,550 yd3(336,840 m3) (Itaipu Binacional 1981). Therecord monthly placing rate of 328,500 yd3(250,200 m3) forroller-compacted concrete was achieved at Tar
26、bela Dam inPakistan. Lean mixtures are now made workable by meansof air entrainment and other chemical admixtures and the useof finely divided pozzolanic materials. Water-reducing,strength-enhancing, and set-controlling chemical admixturesare effective in reducing the required cement content to amin
27、imum and in controlling the time of setting. Placing ratesfor no-slump concrete, by using large earth-moving equipment fortransportation and large vibrating rollers for consolidation,appear to be limited only by the size of the project and itsplants ability to produce concrete.1.2.1 Before 1900Befor
28、e to the beginning of the twentiethcentury, much of the portland cement used in the UnitedStates was imported from Europe. All cements were verycoarse by present standards, and quite commonly they wereunderburned and had a high free lime content. For dams ofthat period, bank-run sand and gravel were
29、 used without thebenefit of washing to remove objectionable dirt and fines.Concrete mixtures varied widely in cement content and insand-coarse aggregate ratio. Mixing was usually done byhand and proportioning by shovel, wheelbarrow, box, or cart.The effect of the water-cement ratio (w/c) was unknown
30、, andgenerally no attempt was made to control the volume ofmixing water. There was no measure of consistency except byvisual observation of the newly mixed concrete.Some of the dams were of cyclopean masonry in which“plums” (large stones) were partially embedded in a verywet concrete. The spaces bet
31、ween plums were then filledwith concrete, also very wet. Some of the early dams werebuilt without contraction joints and without regular lifts.There were, however, notable exceptions where concretewas cast in blocks; the height of lift was regulated, andconcrete of very dry consistency was placed in
32、 thin layersand consolidated by rigorous hand tamping.Generally, mixed concrete was transported to the forms bywheelbarrow. Where plums were employed in cyclopeanmasonry, stiff-leg derricks operating inside the work areamoved the wet concrete and plums. The rate of placementGUIDE TO MASS CONCRETE 20
33、7.1R-3was, at most, a few hundred cubic yards (cubic meters) a day.Generally, there was no attempt to moist cure.An exception to these general practices was the LowerCrystal Springs Dam, completed in 1890. This dam islocated near San Mateo, California, about 20 miles (30 km)south of San Francisco. A
34、ccording to available information,it was the first dam in the United States in which themaximum permissible quantity of mixing water wasspecified. The concrete for this 154 ft (47 m) high structurewas cast in a system of interlocking blocks of specified shapeand dimensions. An old photograph indicat
35、es that handtampers were employed to consolidate the dry concrete(concrete with a low water content and presumably very lowworkability). Fresh concrete was covered with planks as aprotection from the sun, and the concrete was kept wet untilhardening occurred.1.2.2 1900 to 1930After the turn of the c
36、entury,construction of all types of concrete dams was greatly accel-erated. More and higher dams for irrigation, power, andwater supply were built. Concrete placement by means oftowers and chutes became common. In the United States, theportland cement industry became well established, andcement was
37、rarely imported from Europe. ASTM specificationsfor portland cement underwent little change during the first30 years of the century, aside from a modest increase in finenessrequirement determined by sieve analysis. Except for the limitson magnesia and loss on ignition, there were no chemicalrequirem
38、ents. Character and grading of aggregates were givenmore attention during this period. Very substantial progress wasmade in the development of methods of proportioning concrete.The water-cement strength relationship was established byAbrams and his associates from investigations before 1918,when Por
39、tland Cement Association (PCA) Bulletin 1 appeared(Abrams 1918). Nevertheless, little attention was paid to thequantity of mixing water. Placing methods using towers andflat-sloped chutes dominated, resulting in the use of excessivelywet mixtures for at least 12 years after the importance of the w/c
40、had been established.Generally, portland cements were employed withoutadmixtures. There were exceptions, such as the sand-cementsused by the U.S. Reclamation Service (now the U.S. Bureauof Reclamation USBR) in the construction of the ElephantButte Dam in New Mexico and the Arrowrock Dam in Idaho.At
41、the time of its completion in 1915, the Arrowrock Dam, agravity-arch dam, was the highest dam in the world at 350 ft(107 m). The dam was constructed with lean interior concreteand a richer exterior face concrete. The mixture for interiorconcrete contained approximately 376 lb/yd3 (223 kg/m3)of a ble
42、nded, pulverized granite-cement combination. Thecement mixture was produced at the site by intergrindingapproximately equal parts of portland cement and pulverizedgranite so that no less than 90% passed the No. 200 (75 m)mesh sieve. The interground combination was considerablyfiner than the cement b
43、eing produced at that time.Another exception occurred in the concrete for one of theabutments of Big Dalton Dam, a multiple-arch dam built bythe Los Angeles County Flood Control District during thelate 1920s. Pumicite (a pozzolan) from Friant, California,was used as a 20% replacement by mass for por
44、tland cement.During this period, cyclopean concrete went out of style.For dams of thick section, the maximum size of aggregate formass concrete was increased to as large as 10 in. (250 mm).The slump test had come into use as a means of measuringconsistency. The testing of 6 x 12 in. (150 x 300 mm) a
45、nd 8x 16 in. (200 x 400 mm) job cylinders became common prac-tice in the United States. European countries generallyadopted the 8 x 8 in. (200 x 200 mm) cube for testing thestrength at various ages. Mixers of 3 yd3(2.3 m3) capacitywere commonly used near the end of this period, and therewere some of
46、 4 yd3(3 m3) capacity. Only Type I cement(normal portland cement) was available during this period.In areas where freezing-and-thawing conditions were severe,it was common practice to use a concrete mixture containing564 lb/yd3(335 kg/m3) of cement for the entire concretemass. The construction pract
47、ice of using an interior mixturecontaining 376 lb/yd3(223 kg/m3) and an exterior facemixture containing 564 lb/yd3(335 kg/m3) was developedduring this period to make the dams face resistant to thesevere climate and yet minimize the overall use of cement.In areas of mild climate, one class of concret
48、e that containedamounts of cement as low as 376 lb/yd3(223 kg/m3) wasused in some dams.An exception was the Theodore Roosevelt Dam builtduring the years of 1905 to 1911 in Arizona. This damconsists of a rubble masonry structure faced with roughstone blocks laid in portland cement mortar made with ac
49、ement manufactured in a plant near the dam site. For thisstructure, the average cement content has been calculated tobe approximately 282 lb/yd3(167 kg/m3). For the interior ofthe mass, rough quarried stones were embedded in a 1:2.5mortar containing approximately 846 lb/yd3(502 kg/m3) ofcement. In each layer, the voids between the closely spacedstones were filled with a concrete containing 564 lb/yd3(335 kg/m3) of cement, into which rock fragments weremanually placed. These conditions account for the very lowaverage cement content. Constructi
